If your period is delayed for four days and your stomach is swollen, consider if it is related to pregnancy if you have sexual intercourse. It is recommended to check the blood chorionic gonadotropin level at the hospital, if it is higher than normal further examination is needed. The reason is that whether it is an intrauterine pregnancy with preterm miscarriage or an ectopic pregnancy, there will be pain and discomfort in the stomach, and if it is an ectopic pregnancy, it is more dangerous and needs to be hospitalized for further treatment. If pregnancy is excluded, consider the delay of menstruation, the normal menstrual cycle is affected by various reasons such as emotions, may appear delayed menstruation, do not need to be too nervous. It is recommended to adjust your living condition, eat reasonably, quit smoking and drinking alcohol, drink less coffee, do physical exercise and relax.